Battery device for electronic apparatus with rechargeable secondary battery, fuel cell and run time computing unit

1. An electronic apparatus comprising: a power supply unit, a power management unit, a display unit, a first secondary battery interface, and a separable battery device, wherein: said power management unit causes information representative of a run time of said separable battery device to be indicated on said display unit, and said separable battery device comprises: a rechargeable secondary battery adapted to supply power to said power supply unit, a second secondary battery interface, coupled to said first interface, a fuel cell to supply power to said power supply unit, and a battery run time computing unit receiving, from said rechargeable secondary battery, data representative of a characteristic of voltage versus residual-capacity of said rechargeable secondary battery and receiving, from said fuel cell, data representative of a residual capacity of said fuel cell, wherein: said battery run time computing unit determines data representative of a residual capacity of said rechargeable secondary battery and a run time of said rechargeable secondary battery in accordance with said data representative of the characteristic of voltage versus residual-capacity and with supply voltage and supply current of said rechargeable secondary battery, determines a run time of said fuel cell in accordance with said data representative of the residual capacity of said fuel cell and with supply current of said fuel cell, and estimates which of the respective power capacities of said rechargeable secondary battery and said fuel cell reaches a corresponding one of the respective, predetermined residual capacities earlier, if it is estimated that the power capacity of said fuel cell reaches its predetermined residual capacity earlier, said battery run time computing unit determines a run time of said separable battery device, in accordance with said data representative of the rechargeable secondary battery residual capacity, said data representative of the fuel cell residual capacity, and said respective supply currents of said rechargeable secondary battery and of said fuel cell, if it is estimated that the power capacity of said rechargeable secondary battery reaches its predetermined residual capacity earlier, said battery run time computing unit determines the run time of said separable battery device in accordance with the run time of said rechargeable secondary battery, and said battery run time computing unit supplies data representative of the thus determined run time of said separable battery device to said power management unit through said second secondary battery interface and said first interface.

2. The electronic apparatus according to claim 1 , wherein said power management unit causes said data representative of the determined run time of said separable battery device to be indicated on said display unit, as information representative of the run time of said separable battery device.

3. The electronic apparatus according to claim 1 , wherein said separable battery device comprises further a first detector for detecting the supply voltage and current from said rechargeable secondary battery, and a second detector for detecting the supply current of said fuel cell; and said battery run time computing unit determines the respective run times of said rechargeable secondary battery and of said fuel cell, in accordance with the supply current values detected by said first and second detectors, when said electronic apparatus is operating, and said battery run time computing unit determines the respective run times of said rechargeable secondary battery and of said fuel cell, in accordance with predetermined supply current values, when said electronic apparatus is not operating.

4. The electronic apparatus according to claim 1 , wherein said separable battery device comprises further an information converting unit converting, in accordance with said data representative of the characteristic of voltage versus residual-capacity, data representative of the determined run time of said separable battery device into corresponding voltage and current values of said rechargeable secondary battery.

5. The electronic apparatus according to claim 1 , wherein said separable battery device comprises, further, a residual capacity indication unit indicating one or both of the residual capacities of said rechargeable secondary battery and of said fuel cell.

6. The electronic apparatus according to claim 1 , wherein said separable battery device includes a first portion connectable to said electronic apparatus, and a second portion connectable to said first portion, said first portion including said second secondary battery interface and said battery run time computing unit, said second portion including said fuel cell and being separable from said first portion.

7. The electronic apparatus according to claim 1 , wherein said separable battery device comprises further a charging and discharging control unit controlling charging of said rechargeable secondary battery from said fuel cell; and said battery run time computing unit computes a time required for charging said rechargeable secondary battery from said fuel cell to a level required for said electronic apparatus to operate for a given time period.

8. An electronic apparatus, comprising: a power supply unit, a power management unit, a display unit, a first interface for a rechargeable secondary battery, and a separable fuel cell device, wherein: said power management unit operates to cause information representative of a run time of said fuel cell device to be indicated on said display unit; said fuel cell device comprises: a second interface for a rechargeable secondary battery, said second interface being adapted to be coupled to said first interface, a storage device storing therein data representative of the rechargeable secondary battery characteristic of voltage versus residual-capacity, a fuel cell adapted to supply power to said power supply unit, and a fuel cell run time computing unit receiving, from said storage device, said data representative of the characteristic of voltage versus residual-capacity, and receiving, from said fuel cell, data representative of a residual capacity of said fuel cell, wherein said fuel cell run time computing unit determines a run time of said fuel cell in accordance with said data representative of the fuel cell residual capacity and with a supply current of said fuel cell, and supplies data representative of the determined run time of said fuel cell to said power management unit via said second secondary battery interface and said first interface.

9. A separable battery device connectable to supply power to an electronic apparatus, said separable battery device, comprising: a rechargeable secondary battery adapted to supply power to said electronic apparatus, an interface for said rechargeable secondary battery, said interface being adapted to interface with said electronic apparatus, a fuel cell adapted to supply power to said electronic apparatus, and a battery run time computing unit receiving, from said rechargeable secondary battery, data representative of a characteristic of voltage versus residual-capacity of said rechargeable secondary battery, and receiving from said fuel cell, data representative of a residual capacity of said fuel cell, wherein: said battery run time computing unit determines data representative of a residual capacity of said rechargeable secondary battery and a run time of said rechargeable secondary battery in accordance with said data representative of the characteristic of voltage versus residual-capacity and with supply voltage and supply current of said rechargeable secondary battery, determines a run time of said fuel cell in accordance with said data representative of the residual capacity of said fuel cell and with supply current of said fuel cell, and estimates which of respective power capacities of said rechargeable secondary battery and said fuel cell reaches a corresponding one of predetermined residual capacities earlier, if it is estimated that the power capacity of said fuel cell reaches its predetermined residual capacity earlier, said battery run time computing unit determines a run time of said separable battery device, in accordance with said data representative of the rechargeable secondary battery residual capacity, said data representative of the fuel cell residual capacity, and said respective supply currents of said rechargeable secondary battery and of said fuel cell, if it is estimated that the power capacity of said rechargeable secondary battery reaches its predetermined residual capacity earlier, said battery run time computing unit determines the run time of said separable battery device in accordance with the run time of said rechargeable secondary battery, and said battery run time computing unit supplies data representative of the thus determined run time of said battery device to the electronic apparatus through said interface.